Thermal development apparatuses performing the thermal development process of forming a latent image in a sheet film of a photothermographic material and heating the film to develop the latent image to visualize the image are commonly known, in which the sheet film stored in a container is picked-up to convey and supply the sheet film downstream. Conventionally, a vacuum pad system has been adopted, in which sheet film is lifted up, while performing vacuum adsorption of the sheet film by a pad. However, such a vacuum pad system in which the time required for pickup becomes longer, cannot be chosen from the point of view of requirement for rapid access of the thermal development process.
To minimize the time required for pickup for the reason described above is preferred a feed roller system, in which sheet film is fed by bringing a roller into contact with the uppermost sheet film, as described, for example, in U.S. Pat. No. 5,660,384.
However, when plural sheets of film stacked in a container are each fed by a feed roller, the sheet film to be fed is moved in the direction parallel to the film, while being in contact with the lower film and being rubbed, producing problems that abrasion easily occurs.
On the other hand, in photothermographic materials is known adjustment of friction factor by the use of lubricants for improvement of transportability, as described in, for example, JP-A Nos. 2004-219794 and 2004-334077 (hereinafter, the term, JP-A refers to Japanese Patent Application Publication).
However, performing rapid thermal processing by using a thermal processor using a roller pickup for sheet film instead of conventional pickup of a vacuum pad resulted in internal staining of the thermal processor or abrasion of the sheet film, deteriorated transportability and increased variation of density due to change of humidity. There is also desired improvement of density variation accompanied with change in transportability under low humidity or with humidity change.